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Several tests were conducted to study the effect of removing PP component from the fabrics on performance of the fabrics. Fabric structure (observed by light microscope and SEM), fabric specification, water absorption (vertical wicking test), drapability (bending length) and mechanical (ball burst strength test) properties of the fabrics were conducted.

3.12.1

Sample preparation

Prior to testing, samples for each testing were prepared and cut as shown in Figure 3.19. At least 3 samples for each test were prepared.

Figure 3.19 Template for sample size on top of the treated fabric.

3.12.2

Fabric specification

The physical properties of fabric such as fabric mass per area, thickness, number of courses and wales per inch and sticth density were measured.

a) Fabric mass per area

Mass per unit area of the fabrics was assessed using ASTM D3776-09 (2002) Option C – small swatch of fabric. The sample size was modified due to the limited fabric size obtained. Three samples with each having an area at least 38.5 cm2 _{were prepared. The samples were weight on digital balance}

(AdventurerTM _{Ohaus) and recorded in gram (g). Fabric mass per unit area}

was calculated based on Eq. 3.11.

𝑀𝑎𝑠𝑠 𝑝𝑒𝑟 𝑎𝑟𝑒𝑎 𝑔 𝑚⁄ 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒, 𝑔

𝑠𝑎𝑚𝑝𝑙𝑒 𝑎𝑟𝑒𝑎 𝑚 Eq. 3.11

Bending length Vertical wicking test (9 x 2.5 cm) Stitch density Microscopy images (1 in x 1 in) Fabric weight Fabric thickness Ball burst strength (d = 7 cm)

b) Fabric thickness

Fabric thickness were measured using BS EN ISO 5048-1996 on Shirley Thickness Gauge. Three samples of each fabric having an area at least 38.5 cm2 _{were prepared. The sample was placed between the reference plate and}

circular presser-foot equipped with 50 g pressure load. The distance between the reference plate and the circular presser-foot was recorded after 5 s.

c) Courses per inch (CPI), wales per inch (WPI) and stitch density

CPI and WPI of the untreated and treated fabric were measured with magnifying glass. The sample size 1 x 1 in was prepared according to the course and wales wise of the fabric. Then the samples were placed under magnifying counting glass and the CPI and WPI were counted and recorded. The loop created horizontal to the fabric is called course.Wales is the loop produced by the same needle and are vertical to the fabric as shown in Figure 3.20. The stitch density of the fabric is measured by Eq. 3.12. Stitch density represents the looseness or tightness of the fabric; the higher the value, the denser the fabric.

Figure 3.20 Course and wale of knitted fabric.

3.12.3

Fabric structure

The structure of the untreated and treated fabrics was view under light microscope (Leica M205C) and SEM. The procedure for this images is the same as procedure mentioned in section 3.4 (Microscopy).

3.12.4

Bending length

Bending length is related to the rigidity of the fabric, thus influences the drapability and the handle of the fabric. Common test to measure the fabric bending length is cantilever test where the length of the fabric deforms under its own weight was recorded. However, the PP-40 knitted fabrics produced in this study are stiff and tend to curl and twisted during cantilever test, therefore difficult to record the bending length. Other method suggested by (Peirce et al., 1930) is the hanging loop test which is done by clamping the two end of the fabrics and hung downward vertically to form loop shape. Three different loop shapes: ring, pear or heart shape can be used. The hanging pear loop test was chosen considering the limited fabric length obtained and method suitable for stiff fabric.

In this test, rectangular samples with 9 cm length (L) and 2.5 cm width were prepared. The end of the fabric strip was clamped and hung downward as shown in Figure 3.21. The vertical distance from the clamp to the bottom of the loop was recorded as the height of the loop, h. At least 3 samples were measured to get the average value of the loop height in course and wale directions.

Figure 3.21 Hanging pear loop illustration.

3.12.5

Vertical wicking test

The ability of the fabric to transport liquid was conducted by measuring the vertical wicking behaviour in course and wale direction. At first, a wicking solution consists of distilled water, Azonine Scarlet 4BS red dye (0.15 g/l) and non-ionic detergent (0.12 g/l) was prepared. The samples were hung and with the bottom samples immersed in the solution as shown in Figure 3.22. The rise in height was recorded after 30 mins.

However, we found out that the water and dye were separated on samples during wicking testing. The separated components make it difficult to record the height of the solution. Second method was prepared by giving a colour to the samples before immersing them in a dye bath as shown in Figure 3.23.

Figure 3.22 Vertical wicking test using wicking solution.

Before the test, both untreated and treated fabrics were coloured/dyed into red colour using different method, based on the outer component of the fibres. The untreated fabric which has PP as an outside component and PA6 located inside of the fibres were dyed with red dispersed dye. The dyeing process was conducted in Roaches Pyrotec 200 lab dye machine for 3 h at 100 °C. The treated fabrics, which only hasve PA6 microfibres as a component were easily dyed by immersing in the dye solution (0.15g/l Azonine Scarlet dye dissolved in 1 litre distilled water) for 30 mins. The rectangular samples with 9 x 2.5 cm measurement were prepared for this test. The samples were hung vertically with their lower part dipped in the distilled water (Figure 3.23). The height of the water absorbed by the fabric was recorded for 5, 10, 15 and 30 minutes. Six samples for each fabric: three in course and wale direction, respectively, were used in this test.

Figure 3.23 Vertical wicking test using water.

3.12.6

Ball burst strength

To evaluate the strength of the fabric, Titan ball burst strength test was used by using 25.4 mm ball probe and ball burst tooling clamp as shown in Figure 3.24. Three samples from each fabric were used to get the average value of the fabric strength in Newton (N). The fabrics were conditioned at 20±2°C and a relative humidity of 65±5% for at least 24 h before testing.

Production of partially miscible hybrid fibres of polyamide 6

and thermoplastic polyurethane polymer